Nowadays, mobile electronic devices, such as mobile phones, personal digital assistants (PDAs), laptop computers, MP3 players and so on, are in widespread use around the world. Mobile electronic devices are getting smaller and lighter for even more portability and convenience, while at the same time are becoming increasingly capable of performing more advanced functions and services, both due to the development of the devices and the network systems.
For the sake of convenience it is often desirable that these devices are small and lightweight; however, they still need to possess a certain structural strength, so that they are not damaged by normal handling and occasional drops. Thus, usually built into such devices are structural parts whose primary function is to provide strength and/or rigidity and/or impact resistance to the device, and possibly also provide mounting places for various internal components of the device and/or part or all of the mobile electronic device case (outer housing). While in the past, low density metals such as magnesium or aluminum were the materials of choice for such structural parts, synthetic resins have progressively at least partially replaced such metals for reasons of cost reduction, design flexibility, weight reduction, and aesthetic properties. Another problem associated to the use of metals in electronic devices is that they are not transparent to radiofrequencies; therefore, an electronic device cannot be covered with a metal. Plastic parts of electronic devices are hence made of materials that are easy to process into various and complex shapes, are able to withstand the rigors of frequent use, including outstanding impact resistance, and which can meet challenging aesthetic demands while not interfering with their intended operability.
Nevertheless, in certain cases not all the structural parts of mobile electronic devices can be replaced with plastic materials and metal/synthetic resins assemblies are often encountered. In such cases, metal parts, e.g. aluminum parts and/or aluminum/plastic composite parts present in mobile devices are submitted generally to anodization, i.e. to electro chemical processes whose aim is to build an oxide layer on the aluminum surface, notably through the use of aggressive chemicals. In view of the fact that anodization is performed on parts already comprising/assembled into polymeric elements, the polymeric materials must be highly resistant to aggressive acids.
An additional requirement for plastics materials used in mobile electronics part is that they are resistant to consumer chemicals and staining agents that often come into contact with them, in particular with the housings. Typical consumer chemicals and staining agents include: lotions (hand lotions, sunscreen lotions, etc.), makeup (such as lipstick, lip gloss, lip liner, lip plumper, lip balm, foundation, powder, blush), food (olive oil, coffee, red wine, mustard, ketchup and tomato sauce), dyes and pigments (such as those found in dyed textiles and leather used for the manufacture of portable electronic devices housings). In contact with these staining agents, the portable electronic devices housings maybe easily stained: anti-stain properties are hence desired for maintaining good aesthetic appearance of said devices, in particular when they are white or have bright or clear colors.
Exposure to consumer chemicals can lead to premature failure and/or environmental stress cracking of the part if the chemical resistance of the plastic material is not sufficient.
In addition, polymeric materials should possess excellent impact resistance for use in electronic devices; however, the addition of coloring agents such as titanium dioxide (TiO2) may in some instances result in decreased toughness.
There is therefore the need to provide plastic materials which, in addition to possessing high impact resistance and good aesthetic properties, exhibit high chemical resistance.